Cooled multi-component piston for internal combustion engines

ABSTRACT

A cooled multi-component piston is provided in which the hollow annular space in the piston head for the cooling oil is closed off underneath. This is achieved with a sheet-metal ring with a collet which fits in a recess in the piston-ring wall, the sheet metal ring being biased via a retaining clip against the shaft bush.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooled multi-component piston forinternal combustion engines.

2. The Prior Art

This type of piston is known, for example, from DD 2 638 A. In thisknown piston, the annular wall parts for covering an annular coolingduct are slotted rings which are installed under stress on the inside oroutside thereof. An axial stressing of the ring is present to someextent as well. To the extent to which the rings are axially stressedeither on the inside or outside, the edge of the ring that is in eachcase radially removed from the clamping point is axially unsupported.

SUMMARY OF THE INVENTION

It is an object of the present invention to create an annular cover wallwhich, at the same time, is radially safely locked on the inside andoutside against axial displacement. Furthermore, the cover wall issecured in a simple, destruction-free and operationally safe manner.

The above object is achieved according to the present invention byproviding that the annular wall part, which is divided on itscircumference into at least two separated annular segments, has radiallyboth on the inside and outside a collet extending all around. With thiscollet, it engages radially on the inside and outside with radialclamping, in mating, form-locking recesses on the inner circumference onthe outer annular rib of the piston and in the boss support disposedwithin the piston, respectively. In this regard, radial clamping isachieved through an elastic deformation of the collets in the directionperpendicular to the longitudinal axis of the piston.

According to the solution of the prior art problem by the piston of theinvention, such elastic deformation of the collets in the installedcondition constitutes a very important feature. Due to its accommodationon the inside and outside, the wall part can be safely secured in asimple way in an elastic snap lock on the head part of the piston.Furthermore, the double clamping permits thin wall thicknesses for thewall part, because the latter has no freely swinging zones, as is thecase with the annular connection part according to the above-mentionedprior art document.

For accomplishing the radial clamping, it is important that provision ismade on the collet for radial slots radially on the inside and outside,so that radially elastic lashings are obtained distributed across thecircumference of the annular wall part. The required elastic clamping ofthe wall part would not be possible with unslotted, through-extendingcollets. This constitutes another difference vis-a-vis the design of anannular cooling duct cover known from the above-mentioned prior artreference.

Furthermore, special importance has to be attributed to the feature thatthe annular wall part is divided on its circumference at least once,i.e., that at least two annular segments are present. Only such divisionpermits using the annular wall part with piston head parts having bosseswhose outside diameters project significantly beyond the inside diameterof the radial inner sealing of the cooling duct, because in such cases,annular covers of the type according to DD 252 638 A cannot beinstalled. Such known annular sealings are radially slotted only once,so that a ring is obtained that is spread open. Such a ring, however, isradially expandable only to a minor extent if it is to retain itsclamping effect and if its material is not to be damaged duringspreading. Such minor measure does in many cases not suffice to assistin mounting such a ring. With the design according to the aforementionedprior art reference, this constitutes a very decisive difference. Thisdifference is serious particularly because a cover ring according to theprior art reference which, for example, is divided into two separatehalves, could not be secured at all in any functionally safe manneraccording to the disclosure of said reference.

The differences and advantages specified above vis-a-vis DD 252 638 Aare valid vis-a-vis U.S. Pat. No. 4,377,967 as well. Moreover, apartfrom the feature according to which the wall part is radially dividedcircumferentially into at least two annular segments, theabove-specified features of distinction are valid also vis-a-vis DE 3643 039 A (which corresponds to U.S. Pat. No. 5,052,280).

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings which discloses an embodiment of the presentinvention. It should be understood, however, that the drawings aredesigned for the purpose of illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows a longitudinal section through a cutout of the head part ofa two-part joint piston; and

FIG. 2 shows a top view of a sheet metal ring clamped in the head partaccording to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With a joint piston, a head part 1 and a shaft are connected articulatedvia piston pin. The shaft and the piston pin are not shown in theexemplified embodiment shown in the drawing.

Turning now in detail to the drawings, FIG. 1 shows a piston head 1 withan outer annular wall 3 containing the grooves for the piston ringsextending from the piston bottom 2. An annular rib 4 connects bosses 5with the bottom 2 radially with a spacing within the annular wall 3. Anannular hollow space 6 exists between the annular rib 4 and the annularwall 3. The hollow space 6 is covered by a wall part in the form of asheet metal ring 7, to form a closed cooling oil space.

The sheet metal ring 7 has an upwardly curved annular surface 8 with thecollets 9 and 10 shaped thereon on the outer and inner circumferences,respectively. The collets 9 and 10, which point downwardly from theupwardly curved annular surface 8, assume in their resting position thecontour shown by broken lines in FIG. 1. The collets 9 and 10, whichpoint downwardly from the upwardly curved annular surface 8, assume intheir resting position the contour shown by broken lines in FIG. 1.After its installation, the sheet metal ring 7 rests under prestresswith its outer collet 9 in a matching recess 11 on the innercircumference of the annular wall 3, on the one hand, and with its innercollet 10 in a matching recess 12 on the outer circumference of theannular rib 4, or boss 5, on the other hand. In order to permit thecollets 9 and 10 to be elastically deformed, they are provided withlongitudinal slots 13 and 14, respectively, distributed on the outer andinner circumferences. These slots extend across the full length of thecollets 9 and 10.

In order to improve the seating of the sheet metal ring 7 in therecesses 11 and 12, the collets 9 and 10 are bent inwardly toward eachother at their open ends 15 and 16. As a safety element mechanism toprevent turning, a nose 17 projecting from the collet 9 is formed on thesheet metal ring 7, and said nose projects into a matching recess 18provided in the annular wall 3.

The sheet metal ring can be made in two parts with separation jointsbeing present, and have the recesses 20 and 21 for the feeding and thedischarging of cooling oil.

For obtaining the required prestress, the sheet metal ring 7 should bemade of an elastic material, for example, spring steel.

With such a design, a tight closure of the annular hollow space 6required for the cooling oil flowing therethrough is obtained for ajoint piston in a constructively simple way.

While only one embodiment of the present invention has been shown anddescribed, it is to be understood that many changes and modificationsmay be made thereunto without departing from the spirit and scope of theinvention as defined in the appended claims.

We claim:
 1. Cooled multi-component piston for use with an internalcombustion engine, comprisinga head part with bosses formed thereon forreceiving a piston pin connecting the piston with a piston rod; an outerannular wall changing at a first end into the bottom of the head partand ending open at its second end for receiving at least one piston ringgroove, and with a hollow space joined up radially on the inside withsaid annular wall and open to the second end of the annular wall, andsurrounding the bosses or their supporting parts extending to the bottomof the head part, which supporting parts comprise an annular rib, saidhollow space being closed approximately at the level of the second endof the annular wall by an annular wall part so as to form a through-flowcooling oil space, whereby the wall part is clamped under prestressbetween supports on the bosses or supporting parts of the head part, andradially on the outside on the annular wall, where it rests freely ineach case, and with a piston shaft connected with the head part only viathe piston pin; the wall part being an annular surface dividedcircumferentially at least once and having an outer collet formed on theouter circumference and having an inner collet formed on the innercircumference, said collets extending all around and being slottedradially on the inside and outside by cuts; and said wall part engagingwith the outer collet formed on the outer circumference in a recess onthe inner circumference of the annular wall, and with the inner colletformed on the inner circumference in a recess of the annular rib. 2.Multi-component piston according to claim 1,further comprising the wallpart having as a safety element against turning at least one noseprojecting into a recess provided on the annular wall and from the outercollet.
 3. Multi-component piston according to claim 1,wherein the endsof the two collets are bent inwardly toward each other. 4.Multi-component piston according to claim 1,wherein the wall partcomprises a sheet metal ring.
 5. Multi-component piston according toclaim 1,wherein the wall part comprises two parts.